Different types of wireless communication systems have been developed to provide different types of services. Some examples of the wireless communication systems include a wireless local area network (WLAN), a wireless wide area network (WWAN) and a cellular network such as universal mobile telecommunication systems (UMTS). Each of these systems have been developed and tailored to provide specific applications for which each system is intended.
With the pervasive adoption of wireless communication networks in enterprise, residential and public domains, continuous connectivity can be supported as the users move from one network to the other. With the emerging “always-on” life style, wireless transmit/receive units (WTRUs), (i.e., mobile stations), are required to support multiple heterogeneous networks. For seamless handover between these networks, an IEEE 802.21 MIH has been proposed.
In the meanwhile, UMA technology provides access to a global system for mobile communication (GSM) and general packet radio services (GPRS) over unlicensed spectrum technologies, such as Bluetooth™ and IEEE 802.11. By deploying UMA technology, service providers can enable subscribers to roam and handover between cellular networks and public and private unlicensed wireless networks using dual-mode WTRUs. With UMA, subscribers receive continuous services as they transition between networks.
However, UMA technology does not address how a particular handover condition arises and how heterogeneous link layers can communicate these conditions to the upper layers handling the handover. Thus, there are no procedures or functionality in UMA to generate triggers toward upper layers. Therefore, there is a need to provide the triggers for handover within the UMA architecture.